Metrics API: Use jsoniter for JSON encoding (#30250)

* QueryMetricsV2: Stream response

Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com>

* API: Use jsoniter instead of standard JSON package

Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com>

pkg/tsdb/models.go

@@ -9,6 +9,7 @@ import (
 	"github.com/grafana/grafana/pkg/components/null"
 	"github.com/grafana/grafana/pkg/components/simplejson"
 	"github.com/grafana/grafana/pkg/models"
+	jsoniter "github.com/json-iterator/go"
 )
 
 // TsdbQuery contains all information about a query request.
@@ -263,5 +264,5 @@ func (df *dataFrames) MarshalJSON() ([]byte, error) {
 		return nil, err
 	}
 
-	return json.Marshal(encoded)
+	return jsoniter.Marshal(encoded)
 }